The present invention relates to an induction furnace serving both for vacuum melting and pressure pouring, in which a furnace cover is replaced and molten metal obtained by vacuum melting in the induction melting furnace can be continuously poured by a pressure pouring.
In the melting of alloys containing metal which is active (hereinafter called active metal), it is indispensable to prevent the oxidation of active metal within the alloys for enhancing the yield of active metal and the ingot quality.
Therefore, a so-called vacuum melting process which has been hitherto used is a method to melt the alloy in an induction melting furnace within an air-tight container which has been vacuum evacuated (hereinafter called a melting furnace), and this method constitutes an effective means for preventing the oxidation of the alloy.
On the other hand, a vacuum casting process to cast the molten metal into a mold which is housed within the same air-tight container is effective as a means to cast the molten metal under a state in which the cleanliness of the vacuum molten metal is preserved, however, the casting within an air-tight container with a limited inside volume will be limited to a so-called ingot making, where such works as casting, scalping, etc. will be needed before the ingot is hot rolled.
In the prior art as mentioned above, as a melting furnace was housed within an air-tight container, there was no effective means for removing slag which has been generated during the vacuum melting, thus it was necessary to limit the raw material to be molten. It was necessary to melt only virgin raw material ordinarily, avoiding the use of scrap for holding the amount of slag generated down to the minimum level. However, as the melting furnace was tilted for taking the molten metal out when the molten metal was cast into a mold, the slag which had been unavoidably generated will be poured into the pouring sprue along with the tilting of the melting furnace and was unavoidably entrained into the mold.
On the other hand, when a large size ingot was needed, it was necessary to provide a large size air-tight container which housed a melting furnace and a mold in a vacuum melting - vacuum casting process, further the vacuum evacuating capacity had to be increased. Therefore, while a casting with a continuous casting method was desirable for manufacturing a large size ingot which could be directly hot rolled from a standpoint of cost competitiveness, a tremendous amount of equipment investment was needed to have an entire continuous casting equipment housed with an air-tight container.
Thus, when a continuous casting was done, the molten metal which had been vacuum melted had to be first poured to a transfer path to a continuous casting equipment such as a spout under the atmosphere or protective ambient atmosphere, where an oxidation at the pouring sprue or in the transfer path was unavoidable together with flow-in of the slag with the tilting of the furnace, which lowered the ingot quality.